Method of manufacturing electroluminescent lamps



Filed Jan. 311 1956 BY klrraR/vfy J. A. DOMBROWSKI Sept. 9, 1958 METHOD OF MANUFACTURING ELECTROLUMINESCENT LAMPS United States Patent Ofitice METHOD OF MANUFAQTURING ELECT R- LUMINESCENT LAMPS Syla corpora Application January 31, 1956, Serial No. 562,468 4 Claims. (Cl. 117-33.5)

This invention relates to the manufacture of electroluminescent lamps and more particularly to a method for providing said lamps with a layer of dielectric material within which an electroluminescent phosphor is disposed.

In the manufacture of electroluminescent lamps of the plaque type for example, the lamp usually comprises a base member, a conductive coating on a surface of the base 'member, a layer of dielectric material within which an electroluminescent phosphor is disposed over the conductive coating, and a conductive coating over the layer of dielectric material. Care must be exercised in the preparation, application and treatment of the layer of ceramic material within which the electroluminescent phosphor is disposed in order to insure uniformity thereof. For example, the thickness of this layer must be controlled accurately because the brightness of the lamp and the break-down voltage of the medium in which the electroluminescent phosphor is disposed are functions thereof.

An object of this invention is to provide an electroluminescent lamp with a uniform layer of dielectric material within which an electroluminescent phosphor is disposed.

Another object is to provide a method for applying a mixture of electroluminescent phosphor and a dielectric material to a lamp base member during the manufacture of an electroluminescent lamp.

These and other objects, advantages and features are obtained, in accordance with the principles of our invention by applying a paste, comprising an electroluminescent phosphor and a dielectric material disposed in a suitable vehicle, to a base member of an electroluminescent lamp through a screen. Application of the paste is effected by drawing a quantity of the paste across the screen with a suitable tool, such as a squeegee for exam ple. The screen is then removed, leaving a deposit of the paste on the lamp base member. Thereafter the paste is heated to drive oif the vehicle, thus leaving a layer of a mixture of electroluminescent phosphor disposed in a dielectric medium.

One type of apparatus, with invention may be practiced, panying drawings in which:

Figure l is a perspective view lamp base member seated thereon;

Figure 2 is a perspective view thereof, showing the screen, through which the paste is forced, in position on top of the lamp base member;

Figure 3 is a perspective view thereof, showing the manner in which a body of the paste is drawn across the screen to force a quantity thereof through the screen to the lamp base member;

Figure 4 is a perspective view of the lamp base member with a layer of the phosphor-dielectric thereon.

Referring now to Figure 1, the apparatus shown therein, with which the method of this invention may be employed, comprises a base 10, a seat 12 centrally located thereon on which a lamp base member 13 may be posiwhich the method of this is illustrated in the accomthereof, showing the Patented Sept.'9, 1958 tioned, a frame 14, within which a screen 16 is mounted, attached to the base 10 by hinges 18, and a pair of screws 20 in hinges 22 attached to the base 10.

In the practice of the method of this invention with the apparatus shown in the drawings, a lamp base member 13 is positioned on the seat 12 of the frame 14 is moved from its position as shown in Figure l to its position as shown in Figure 3, thereby bringing the screen 16 into contact with the top surface of the lamp base member 13. The screws 20 are then turned down to secure the screen 16 in engagement with the lamp base member 13. A quantity of paste 24 is placed on a masked portion 17 of screen 16 and a suitable tool, such as squeegee 26 (Fig. 3) is employed to draw the paste 24 across the screen 16 and force it through the screen onto the lamp base member 13. The screen 16 is then removed, leaving a deposit of the paste 24 on the lamp base member 13. The layer of paste 24 is then heated to drive off the vehicle leaving a layer of dielectric material with a quantity of electroluminescent phosphor embedded therein. When a paste of the composition described below is used, heating at about 750 F. for a period of about 20 minutes has been found to be satisfactory. Care must be exercised to insure complete elimination of the vehicle because if an appreciable quantity thereof emains, it will carbonize during the subsequent firing to effect fusion of the ceramic material, and the brightness of the lamp and the break-down voltage of the ceramic material will be affected adversely by the presence of this ash.v

The paste 24 is a mixture of an electroluminescent phosphor and powdered ceramic material disposed in a suitable oil-base vehicle, such as pine oil, and a methyl ester of wood rosin for example. An electroluminescent phosphor, such as a lead-containing copper-activated zinc sulfide prepared in accordance with the method described in U. S. Patent No. 2,728,731 for example, has been found to be particularly satisfactory, although other electroluminescent phosphors known in the art may be employed.

The ceramic material is selected for its capability of fusing or sintering at a temperature below that which would destroy the phosphor during the fusion process. It is preferably free of any appreciable quantities of easily-reducible metallic compounds which would give an undesirable metallic deposit. Ceramic materials of the types disclosed in the copending application of Richard M. Rulon, Serial No. 365,617, filed July 2, 1953, have been found to be satisfactory.

In the preparation of the paste, powdered phosphor and powdered ceramic material are mixed and the vehicle is then added. For example, a particularly satisfactory paste may be obtained by mixing about 28 parts by weight of phosphor powder with about 72 parts by weight of ceramic powder, and then adding about 30 parts by weight of an oil-base thinner to about 70 parts by weight of the phosphor-ceramic mixture. An oil-base thinner which has been found to be particularly satisfactory comprises about 82% pine oil and about 18% methyl ester abietic acid. Variations in the proportions of the above-mentioned ingredients may be made without departing from the spirit of the invention. For example, the quantity of thinner may be varied depending on the desired viscosity of the paste and the desired thickness of the phosphor-ceramic layer.

The wire size and mesh of the screen may also be varied depending on the desired thickness of the layer of ceramic material with the electroluminescent phosphor embedded therein. For example, a layer about .0015 inch thick may be obtained by using a paste of the composition defined above and applying it to the lamp base member through a 200 mesh screen having a wire size of about .0021 inch. A layer about .002 inch thick may be obtained by using a paste of the composition defined above and applying it to the lamp base member through a 150 mesh screen having a wire size of about .0026 inch.

The article illustrated in Figure 4 is a specific example of an electroluminescent lamp as it'appears after it has been provided with thelayer of ceramic material with an electroluminescent phosphor embedded therein. It comprises a metal plate 3, a porcelain coating 5, a conductive coating 7 and a layer 9 of ceramicmaterial with an electroluminescent phosphor embedded therein. Subsequently a transparent conductive coating is applied over layer 9. The conductive coatings are the electrodes, and when an alternating voltage is applied between them, the electroluminescent phosphor embedded therein luminesces. v

The method of this invention may be employed in the manufacture of electroluminescentlamps structurally different from the one just described, For example, the porcelain coating and the conductive coating 7 may be omitted, in which case the metal plate 3 would be one of the electrodes and the layer of ceramic material with the electroluminescent phosphor embedded therein could be applied directly thereto. A glass plate may be used instead of the metal plate 3, the porcelain coating may be omitted and the layer of ceramic material with the electroluminescent phosphor embedded therein may be applied directly to the glass plate.

What I claim is:

1. The method of providing an electroluminescent lamp with a layer of dielectric material within which an electroluminescent phosphor is embedded which comprises: applying a paste, comprising a mixture of electroluminescent phosphor and ceramic material in an oilbase vehicle therefor, to a lamp base member through a screen; and heating the paste so deposited to a temperature sufficient to remove the said vehicle but below the temperature required to effect fusion of the ceramic material.

2. The method of providing an electroluminescent lamp With a layer of dielectric material within which an electroluminescent phosphor is embedded which comprises: applying a paste, comprising a mixture of a leadcontaining copper-activated zinc sulfide electroluminescent phosphor and ceramic material in an oil-base vehicle therefor, to a lamp base member through a screen; and heating the paste so deposited to a temperature sufiicient to remove the said vehicle but below the temperature required to effect fusion of the ceramic material.

3. The method of providing an electroluminescent lamp with a layer of dielectric material within which an electroluminescent phosphor is embedded which comprises: applying a paste, comprising a mixture of electroluminescent phosphor and ceramic material in an oilbase vehicle therefor, to a lamp base member through a screen, said oil-base vehicle comprising about 82% by weight of pine oil and about 18% by weight of methyl ester abietic acid; and heating the paste so deposited to a temperature sufficient to remove the said vehicle but below the temperature required to effect fusion of the ceramic material.

4. The method of providing an electroluminescent lamp with a layer of dielectric material within which an electroluminescent phosphor is embedded which comprises: applying a paste, comprising a mixture of a leadcontaining copper activated zinc sulfide electroluminescent phosphor and ceramic material in an oil-base vehicle therefor, to a lamp base member through a screen, said oil-base vehicle comprising about 82%; by Weight of pine oil and about 18% by weight of methyl ester abietic acid; and heating the paste so deposited'to a temperature sufficient to remove the said vehicle but below the tempera ture required to effect fusion of the ceramic material.

References Cited in the file of this patent UNITED STATES PATENTS 2,312,229 Anderson Feb. 23, 1943 2,559,279 Charles July 3, 1951 2,566,349 Mager Sept. 4, 1951 2,624,857 Mager Jan. 6, 1953 2,625,734 Law Jan. 20, 1953 2,687,360 Michaels Aug. 24, 1954 2,709,765 Koller May 31, 1955 2,721,808 Roberts et al. Oct. 25, 1955 2,721,950 Piper et al. Oct. 25, 1955 2,742,376 Larach Apr. 17, 1956 

1. THE METHOD OF PROVIDING AN ELECTROLUMINESCENT LAMP WITH A LAYER OF DIELECTRIC MATERIAL WITHIN WHICH AN ELECTROLUMINESCENT PHOSPHOR IS EMBEDED WHICH COMPRISES: APPLYING A PASTE, COMPRISING A MIXTURE OF ELECTROLUMINESCENT PHOSPHOR AND CERAMIC MATERIAL IN AN OILBASES VEHICLE THEREFOR, TO A LAMP BASE MEMBER THROUGH A SCREEN; AND HEATING THE PASTE SO DEPOSITED TO A TEMPEARATURE SUFFICIENT TO REMOVE THE SAID VEHICLE BUT BELOW THE TEMPERATURE REQUIRED TO EFFECT FUSION OF THE CERAMIC MATERIAL. 